The present invention relates to tools for retrieving and placing objects within a container, and more particularly relates to such a retriever tool for use when retrieving or mounting test or process elements such as corrosion or temperature probes, test coupons, anodes or the like.
In the processing and handling of fluids, such as for example transport or refining of oil and gas products, fluids often are confined and transported at high temperatures and exceedingly high pressures in closed containers or substantially closed transport systems. Monitoring and testing of the confined fluids, are frequently carried out by the insertion of corrosion monitoring probes, such as those known as the CORROSOMETER and CORRATER corrosion measuring probes, through fittings fixed to openings in the container or pipe walls. Test and processing probes include, among many others, not only corrosion measuring instruments, but temperature measuring instruments, corrosion coupons and anodes providing for cathodic protection. The test or monitoring devices, when inserted into the container, seal the opening and are frequently left in place for long periods of time. However, most have a limited life and must be removed and/or replaced periodically, preferably without shutting down or depressurizing the system being monitored.
Retriever tools developed for retrieving and installing such test or monitoring objects, generally include a pressure resistant housing in which is mounted a long transport shaft that carries a connecting device which is detachably coupled to the probe by suitable manipulation of the transport shaft. A valve is initially connected to the fitting in which the probe is installed, and the tool is connected to the valve in a pressure tight relation so that the valve may then be opened to allow access from the interior of the tool to the probe without loss of pressure, except to the interior of the tool. A transport shaft within the tool is then manipulated, driven forwardly and generally rotated, so as to grasp the probe and remove it from its threaded connection in the pipe access fitting.
A typical retriever tool is shown in U.S. Pat. No. 4,275,592 to Atwood et al., wherein the transport shaft is the form of a long rack which is driven longitudinally of the tool housing to extend through a valve into contact with a probe or coupon holder that is to be removed. Because the transport rack must extend from the tool and through a connecting valve and then be retracted into the closed and sealed body of the tool, the tool has a relatively great length. This length is a major disadvantage because space around the containers and pipes is frequently limited, particularly at points where probes and the like are inserted and positioned. Therefore in many instances it is difficult, if not impossible, to either place the access nipple at a most desired location or to provide access to the probe or the like by a tool of such length.
A devive such as that shown in the patent to Lancaster, U.S. Pat. No. 4,215,458, provides an arrangement where the tool has a decreased length but does so only at the expense of increased diameter and weight.
Retrieving tools of this general type, require at least two separate and independently controllable motions. The first is a run in or run out longitudinal motion which is employed to move the probe longitudinally of the tool, into position at the pipe or container or to remove it from its operating position. A second motion is a rotation of the probe connecting device to rotate the probe so that it may be threaded into and out of the threaded access nipple of the pipe.
The Atwood et al. U.S. Pat. No. 4,275,592 employs a second gear box having a worm and helical gear and a splined connection for effecting rotation. In order to obtain rotation, the arrangement of the patent to Lancaster, U.S. Pat. No. 4,215,458, employs a second shaft, parallel with the longitudinal screw drive, which is gear connected to rotate the longitudinally driven rod member to which the probe is to be connected. The Lancaster patent, like the Atwood el al. patent, involves relatively complex driving gears and gear boxes that are subject to wear and jamming in the presence of debris and other trash that is frequently carried into the tool during its use. Furthermore, the Lancaster arrangement, which actually requires three separate drive rods, inherently requires a larger tool diameter because of the need to accommodate side by side rods. Increased diameter introduces greatly increased forces in a high pressure tool. Wall thickness required to withstand the exceedingly high pressure involved becomes very great and the weight and cost of the tool are significantly increased. Further, the added tool weight and size makes the tool bulky and difficult to handle.
Accordingly, it is an object of the present invention to provide a retriever tool that avoids or minimizes these and other problems.